Method of transferring heat by a hydrocarbon medium



Patented Feb. 21, 1950 METHOD OF TRANSFERRING HEAT BY A HYDROCARBON MEDIU Karl Cohen, New York, N. Y., and Edward H. McArdle, Linden, N. J., assignors to Standard Oil Development Corn Delaware pany, a corporation of No Drawing, Application October 24,1946,

Serial No. 705,430

This invention relates to novel liquid heat transfer media, more particularly to heat transfer media which are composed essentially of highly aromatic petroleum hydrocarbons.

Many different types of materials have been used heretofore for heat transfer purposes, one mixture which has met with considerable success is a mixture of diphenyl and diphenyl oxide. However, this particular mixture solidifies at a temperature which is substantially too high for use in many purposes, for instance in any process which is operated out of doors where the winter climate or cold temperature gets down substan* tially below 10 C. or about 50 F.

One object of the present invention is to provide a highly aromatic petroleum fraction which remains fluid at temperatures as low as F. thereby providing the possibility of its use in apparatus which is used out of doors where temperatures as low as 0 F. may be encountered during the winter-time.

Broadly this invention comprises using a relatively narrow boi ing selective solvent extract of a cycle gas oil. The boiling range should preferably be about 500-600 F. It is an exceedingly highly aromat c fraction and is actually more dense than water, i. e. has a specific gravity greater than 1.0. This fraction possesses the highest thermal stability of any petroleum product of such volatility, and is therefore most suitable as a high temperature transfer medium. It is suitable for both liquid and vapor phase heat transfer.

By the expression cycle gas oil it is intended to mean the gas oil fraction which has been recycled one or more times during a catalytic cracking of a etroleum gas oil stock. During the crackin generally highly aliphatic and marchthenic fractions are cracked and converted into aromatic fractions, and thus bv the recycling process substantially all of the aliphatic or mixed aliphatic aromatic fractions present in the gas oil which can possibly be cracked and. converted into more aromatic stock are actually thus converted and therefore are relatively stable when merel subjected to ordinary heat transfer processes in the absence of any cracking catalyst.

For the purposes of this invention it is possible to use a catalytically cracked cycle gas oil having a relatively broader boiling range and without any solvent extraction, but such a fraction will have relatively limited utility, and therefore 2 Claims. (01. 252-13) it is highly preferred to first subject the crude cracked recycled gas oil to distillation to obtain I a narrow cut fraction boiling from about 500- 600 F., and then preferably to still further-subject that narrow cut distillate to a selective solvent extraction with a solvent which has selective solvency for highly aromatic compounds, as for instance extracting with phenol, liquid sulfur dioxide, furfural, dichlor ethyl ether, nitrobenzene, aniline, or cresols.

As a specific illustration of this invention, a crude gas oil of a petroleum fraction was subjected to catalytic cracking at a temperature of about 950-1000 F. using synthetic aluminum silicate as catalyst, and under a pressure of about 8 lbs/sq. in. gauge pressure. Uncracked material was continuously recycled.

The recycled gas oil thus obtained was distilled to obtain a narrow cut fraction boiling at about 500-600 F., and it was then subjected to selective solvent extraction with phenol at a temperature of about F., using 1 volumes of phenol per volume of gas oil out in an apparatus with countercurrent flow.

After the solvent extraction, the extract was then separated from the phenol by distillation. The resulting phenol-extract had a specific gravity of about 1.05 and had a carbon to hydrogen ratio of 9.9, and a melting point of -24 F. and boiling range of 505 to 585 F.

When the fraction thus obtained is used as a vapor phase heat transfer medium it is stable up to temperatures of about 950 F. When using this novel heat transfer medium, it is intended of course to use it in various ways known to the art, such as by first contacting this heat transfer medium either in the liquid phase or vapor phase with a high temperature zone, such as by passing through steel coils being heated by direct fire in a furnace, or by hot metal bath, or by hot salt bath, or directly by immersed electrically heated strip or wire, subsequently contacting this heated heat-transfer medium with a lower temperature zone, such as a varnish or resin kettle, whereby the heat contained in the heat transfer medium will be transferred to the lower temperature zone. By repeated recycling the heat transfer medium can be used over and over again. Various industrial applications to which this invention is particularly suitable include the following: the heating and subsequent shock-chilling or resin, varnish, and drying oil kettles; the indirect generation of steam; the recovery of volatile solvents; and the transfer of energy from atomic piles. a

It is not intended that this invention be limited to the specific examples which have been given 3 merely for the sake of illustration but only by the appended claims.

We claim:

1. The method of transferring heat at very high temperatures up to about 950 F. which comprises continuously circulating a fiuid heat transfer medium through a closed cycle, applying heat at one portion of said cycle to said medium and removing heat therefrom at another portion of said cycle, in which said medium is a highly aromatic gas oil fraction which has been extracted from a cycle gas oil fraction by a solvent which is selective for aromaticsQsaid medium having a specific gravity greater than 1.0, a solidifying point below 0 F., and a narrow boiling range within the limits of 500.and 600 F.

2. A method as in claim l where the heat transfer medium is a phenol extracted recycled gas oil having a carbon to hydrogen ratio of 9.9 and being highly thermally stable at temperatures up to 950 F.

KARL COHEN. EDWARD H. McARDLE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,573,532 Alexander Feb. 16, 1926 2,228,510 Dearborn et a1 Jan. 14, 1941 2,270,717 Shipp et al Jan. 20, 1942 2,304,289 Tongberg Dec. 8, 1942 2,342,888 Nysewander et al. Feb. 29, 1944 2,363,237 Harvey Nov. 21, 1944 2,374,387 Shipp et a1 Apr. 24, 1945 OTHER REFERENCES Egloff, Reactions of Pure Hydrocarbons," pages 499 and 500, pub. by Reinhold Publishing Corporation, New York, N. Y., 1937. 

1. THE METHOD OF TRANSFERRING HEAT AT VERY HIGH TEMPERATURE UP TO ABOUT 950*F. WHICH COMPRISES CONTINUOUSLY CIRCULATING A FLUID HEAT TRANSFER MEDIUM THROUGH A CLOSED CYCLE, APPLYING HEAT AT ONE PORTION OF SAID CYLE TO SAID MEDIUM AND REMOVING HEAT THEREFROM AT ANOTHER PORTION OF SAID CYCLE, IN WHICH SAID MEDIUM IS A HIGHLY AROMATIC GAS OIL FRACTION WHICH HAS BEEN EXTRACTED FROM A CYCLE GAS OIL FRACTION BY A SOLVENT WHICH IS SELECTIVE FOR AROMATICS, SAID MEDIUM HAVING A SPECIFIC GRAVITY GREATER THAN 1.0, A SOLIDIFYING POINT BELOW 0*F., AND A NARROW BOILING RANGE WITHIN THE LIMITS OF 500* AND 600*F. 